This invention relates to electrical switching apparatus. More particularly, it is concerned with electromagnetically operated switching apparatus employing a plurality of contact modules.
Electrical switching apparatus such as electromagnetic contactors or relays are widely used in industrial control systems. In order to provide versitility contactors of this general type frequently employ switch or contact modules which selectively may be changed to provide either normally open or normally closed circuit conditions. The contact modules are actuated to switch between circuit conditions by appropriately energizing and deenergizing the coil of an electromagnet. When the coil is energized a movable armature moves into contact with a stationary magnet, and when the coil is deenergized the armature is returned to its original position by compression springs. Linkage members couple the movable armature to elements within the contact modules so that movement of the armature between the two positions switches the contact elements of each module to provide the desired open and closed circuits therethrough.
In order to provide for proper operation of the contact modules the distance between the energized and deenergized positions of the movable armature and the positioning of the contact modules with respect to the two positions of the movable armature should be accurately controlled. In switching apparatus heretofore available, however, the aforementioned relationships were determined by the net results of several dimensions of several assembled parts. Because of the accumulation of dimensional errors tight dimensional tolerances were necessary in order to control the relationships within the desired degree of accuracy.